• Korean Journal of Ecology and Environment
• /
• v.52 no.1
• /
• pp.40-49
• /
• 2019

Seasonal succession of zooplankton community and species composition was studied from 2003 to 2014 in a deep reservoir, Lake Soyang, in monsoon climate region, Korea. Annual precipitation was concentrated more than 70% between June and September and it showed remarkably that seasonal variation in water quality. Seasonal variation of water quality in Lake Soyang appeared to be more significant than annual variations, and the inflow of turbid water during the summer rainfall was the most important environmental factor. Zooplankton sepecies composition in Lake Soyang showed obvious tendency through two periods (May to June and August to October) every year. Small zooplankton (rotifer; Keratella cochlearis, Polyarthra vulgaris) dominated in spring and mesozooplankton such as copepods and crustaceans were dominant in summer and fall. Zooplankton biomass showed the maximum in September after monsoon rainfall, and chlorophyll showed a similar seasonal variation and it showed a high correlation (r=0.45). The increase of zooplankton biomass is considered to be a bottom-up effect due to the increase of primary producers and inflow of nutrients and organic matter from rainfall. In this study, we found that the variation of zooplankton community was affected by rainfall in monsoon climate region and inflow of turbid water was an important environmental factor, which influenced the water quality, zooplankton seasonal succession in Lake Soyang. It was also considered to be influenced by hydrological characteristics of lake and environment of watershed. In conclusion, seasonal succession of zooplankton species composition was the same as the PEG model. But seasonal succession of zooplankton biomass differed not only in the temperate lake but also in the monsoon region.

• Journal of Wetlands Research
• /
• v.23 no.2
• /
• pp.189-200
• /
• 2021

To improve the water quality of agricultural reservoirs, constructed wetlands are applied in many places. These are technologies that establish ecosystems and important design factors include water depth distribution, inflow and outflow, water flow distribution, hydraulic residence time, water quality treatment efficiency, aspect ratio, and the distribution of open water and covered water surfaces. For high efficiency during the operation of a constructed wetland, the design needs to be optimized and this requires consideration of the different types and length of the intake dam as well as the type and connection of wetland cells. Therefore, this study was conducted to investigate and suggest factors that needs to be considered during the design and for efficient operation measures through field surveys of 23 constructed wetlands that have been established and operated in agricultural reservoirs. Results of the field investigation shows that several sites were being operated improperly due to the malfunctioning or failure of the water level sensors, sedimentation in the intake dam, and clogging of the mechanical sluice frames. In addition, it was found that as the length of the inlet channel increases, the ecological disconnection between the intake dam upstream and the wetland outlet downstream also increases and was identified as a problem. Most of the wetlands are composed of 2 to 5 cells which can result to poor hydraulic efficiency and difficulty in management if they are too large. Moreover, it was found that the flow through a small wetland can be inadequate when there are too many cells due to excessive amounts of headloss.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2023.05a
• /
• pp.148-148
• /
• 2023

산업 고도화로 인하여 복잡하고 다양한 유기물의 사용량이 증가하였으며, 공공수역 내 새로운 오염물질이 유입됨에 따라 생화학적 산소요구량(BOD) 중심의 수질평가에 한계를 나타내었다. 이후 난분해성 물질을 고려한 유기물관리 정책과 총량관리의 필요성이 제기되었고 국내 하천과 호소에서는 총 유기탄소(TOC)를 유기물 관리지표로 설정하였다. 그러나 부영양 하천과 호소에서 TOC는 외부 부하뿐만아니라 식물플랑크톤의 과잉성장에 의해 증가할 수 있는 항목이므로 TOC 관리정책 추진을 위해서는 유기물의 기원에 대한 파악이 필요하다. 한편, 우리나라와 같이 몬순 기후대에 속한 댐 저수지의 경우 강우시 유입하는 탁수에 의해 다량의 유기물과 인이 유입되기도 하지만 식물플랑크톤의 제한요인 중 광량에 많은 영향을 미친다. 식물플랑크톤의 광합성은 수체 내 유기탄소 내부생성에 매우 중요한 요소이나 점 단위의 실험적 방법을 활용한 유기탄소 순환 해석은 저수지의 시·공간적인 변동성을 고려하기에 한계가 있다. 본 연구의 목적은 금강 수계 최대 상수원인 대청호를 대상으로 3차원 수리-수질 모델을 적용하여 유기탄소 성분 별 유입과 유출, 내부생성 및 소멸량을 평가하고 탁수가 저수지에서의 유기탄소 순환에 미치는 영향을 분석하는데 있다. 유기탄소 물질수지 해석을 위해 AEM3D 모델을 사용하였으며 2018년을 대상으로 입력자료를 구축한 후 보정 및 검정을 수행하였다. 모델은 유기탄소를 입자성, 용존성, 그리고 난분해성과 생분해성으로 구분하여 모의하며 유기물질 성상별 실험결과를 이용하여 입력자료를 구축하였으며 유기탄소순환 해석을 위해 4가지의 탄소성분과 조류 세포 내 탄소의 질량 변화율을 계산하였다. 이를 위해 외부 유입·유출부하율, 수체 내 생성(일차생산, 재부상, 퇴적물과 수체 간 확산) 및 소멸률(POC 및 조류 침강, DOC 무기화, 탈질)을 고려하였으며 탁수의 영향을 분석하기 위해 탁수 포함여부 시나리오를 구성하고 유기탄소 생성 및 소멸기작별 변동성을 비교 분석하였다. 모델은 2018년의 물수지를 적절히 재현하였으며 저수지의 수온 및 탁도 성층구조를 잘 재현해내면서 전반적인 수질을 적절하게 모의하였다. 탁수를 고려하였을 시 연간 TOC 부하량 중 내부기원 부하량은 56% 수준이였으나 탁수를 배제한 경우 내부기원 부하량은 82%로 나타났다. 특히, 연평균 Chl-a 농도가 44~48% 차이가 발생하면서 1차생산량이 약 4배가량 증가하였다. 몬순지역에서의 탁수는 체류시간이 긴 성층 저수지에서 식물플랑크톤 성장제어에 큰 영향을 미쳤으며 전반적인 유기탄소 순환을 해석하는데 있어 매우 중요한 인자로 작용하였다.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2021.06a
• /
• pp.457-457
• /
• 2021

인공습지는 자연이 가진 정화기작을 인위적으로 증가시키기 위하여 조성한 자연기반해법에 해당한다. 인공습지는 습지 내 식물, 미생물, 토양 등의 상호기작에 의하여 오염물질이 제거된다. 인공습지의 오염물질저감효율은 시설의 규모와 유량, 유입물질의 부하량 수리학적 부하량, 체류시간 등의 영향을 받게 된다. 일반적으로 인공습지 적정 규모는 유역 및 기상인자의 특성과 조성목적에 고려하여 산정된다. 본 연구는 전국 35개 지역에 설치된 54개 인공습지를 선정하여 모니터링을 수행하였으며, 2011년부터 2018년에 설치된 시설이다. 54개 시설 중 도심지역에 13개, 농업지역 25개, 공업지역 3개, 상업지역 3개, 축산 10개가 설치되어있다. 습지형태는 Cell형 자유수면형 인공습지(Free Water Surface, Cell-FWS), 유로형(Flow) 자유수면형 인공습지(Cell-FWS), Cell과 Flow형이 결합된 Hybrid-FWS, 수직흐름형 인공습지(vertical flow constructed wetland)와 수평지하흐름형 인공습지(vertical flow constructed wetland)가 결합된 HYBIRD 형 습지로 구분된다. 연구결과, 일반적으로 SA/CA 비율이 클수록 오염물질의 저감효율은 증가하는 것으로 나타났다. 오염 물질별 인공습지 규모를 비교할 경우 저감효율 60%에서 인공습지의 규모는 유기물>영양염류>입자상물질 순으로 나타났다. 목표 제거효율 60%에서 SA/CA 비는 BOD에서 약 3.2%, COD에서 2.5%, SS에서 1.9%, TN 2.5%, TP 2.3%로 나타났다. 입자상물질인 SS는 유기물 및 영양염류에 비하여 유역면적 대비 시설면적이 가장 적게 나타났으며, 유기물질 제거에 큰 시설규모가 필요한 것으로 나타났다. 따라서 인공습지 설계시 유역 토지이용 및 강우특성을 고려하여 적정한 수질과 유량모니터링이 필요하며, 이를 토대로 목표 오염물질 선정이 중요한 것으로 나타났다. 또한, 농업지역의 최적화된 인공습지 위치는 임야가 20~30%, 밭이 20% 이하, 논이 10~50%를 포함하는 곳이 적정한 것으로 평가되었다. 도시지역 인공습지는 도시면적이 증가할수록 효율이 크게 변하지 않기에 가용위치가 적정한 위치로 평가된다. 인공습지의 효율은 유역의 세부 토지이용에 크게 의존하는 것으로 평가되었다. 따라서 인공습지 설계시 농업지역에서는 임야, 밭 및 논의 적정면적을 고려하여 인공습지 위치가 결정되어야 하는 것으로 나타났다.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
• /
• v.15 no.4
• /
• pp.192-202
• /
• 2010

Submarine groundwater discharge (SGD) has been recognized as a provider for freshwater, nutrients, and dissolved constituents from continents to the oceans and paid more attention with regard to the mass balance of water or dissolved constituents on local and global scales. The submarine discharge of fresh groundwater (fresh SGD) through seepage or springs in coastal ocean may be especially important in aspects of water resource and marine environment managements in the future. Based on the worldwide compilations of observed fresh SGD, our review reveals that fresh SGD occurs in various marine environments along most shoreline of the world and the global estimates of fresh SGD were approximately 0.01-17% of surface runoff. In addition, the input of fresh SGD calculated and investigated in this study were about 50%, 57%, 89%, and 420% of total river discharge in Jeju Island, Yeongil Bay, Masan Bay, and Yeoja Bay, respectively. These inputs from fresh SGD along the shoreline of Korea Peninsula are much higher than those of the whole world, greatly vary with the region. However, since these estimates are based on the water balance method mainly used in coastal ocean, we have to perform continuous monitoring of various parameters, such as precipitation, tide, evapotanspiration and water residence time, which have an impact on the water balance in a lot of areas for evaluating the precise input of fresh SGD. In addition, since the method estimating the input of fresh SGD has brought up many problems, it is required to make an intercomparison between various methods such as hydrogeological assumption, numerical modeling, and seepage meter.

• Korean Journal of Ecology and Environment
• /
• v.34 no.1 s.93
• /
• pp.9-19
• /
• 2001

contrasting monsoon between 1993 and 1994 produced an interannual difference in hydrology. Theoretical water residence time (TWRT) in monsoon 1993 averaged 27 d, which was>3 months shorter compared to the TWRT in monsoon 1994. A dominant physical process influencing thermal stratification, water movement, and mixing regime was an interflow current in 1993. During summer 1993, river water plunged to mid-lake (location 27 km) and passed through the 10${\sim}$20m stratum of the reservoir, resulting in an isolation of epilimnetic lake water from advected river water. The interflow disrupted thermal stratification and produced a meta-hypolimnetic warming of >4$^{\circ}C$ downlake, thereby increased a mixing depth (>13 m). In contrast, during monsoon 1994 density currents were not observed and strong thermal stratification occurred in the entire reservoir, resulting in > 2 fold greater thermal resistance (8.2${\times}10^{5}$ erg)compared to 1993 (4.0${\times}10^{5}$ erg). This reservoir was identified as a typical warm monomictic reservoir which showed one mixis during early winter. The timing of overturn, however, differed between the two years as a result of distinct contrast in TWRT and thermal regime; overturn in 1993 occured about one month earlier relative to that in 1994. Hypolimnetic warming was predictable in this system; the variation in discharge accounted (Y = 4.35-0.06X+0.10X$^{2}$, p<0.0001)for 98% of the interannual variation in hypolimnetic temperature. Overall data suggest that thermal stability, the timing of fall overturn, and water residence time in this system are primarily regulated by the intensity of monsoon.

• Journal of Korean Society of Environmental Engineers
• /
• v.22 no.4
• /
• pp.797-806
• /
• 2000

The objectives were to compare the biodegradable threshold concentrations of phenol with the different composition of the influent carbon source and examine the SMA (Specific Methanogenic Activity)and the possibility of simultaneous removal of high-strength organics and nitrogen compounds in UASB(Upflow Anaerobic Sludge Blanket) - PBR(Packed Bed Reactor) process. The results showed that UASB reactors were efficient to remove phenol and phenol + glucose from synthetic wastewater. At phenol conc, of 600 mg/L and SCOD conc. of 2100 mg/L in UASB reactor(with only phenol as substrate), the removal efficiencies of phenol and SCOD were over 99% and 93% respectively, under MLVSS of 20 g. The activity of microorganism was $0.112g\;phenol/g\;VSS{\cdot}d$, $0.351g\;SCOD/g\;VSS{\cdot}d$. The gas production rate was $0.115L/g\;VSS{\cdot}d$ and $CH_4$ content in gas was about 70%. At phenol conc. of 760 mg/L and SCOD conc. of 4300 mg/L in UASB reactor( with phenol + glucose as substrates), the removal efficiencies of phenol and of SCOD were over 99% and 90% respectively, under MLVSS of 20 g. The activity of microoganism was $0.135g\;phenol/g\;VSS{\cdot}d$, $0.696g\;SCOD/g\;VSS{\cdot}d$. The gas production rate was $0.257L/g\;VSS{\cdot}d$ and $CH_4$ content in gas was about 70%. Serum bottle test showed that the activity of granule was inhibited over 1600 mg/L phenol conc, and denitrification and methanogenesis simultaneously took place in UASB granules under co-substrates conditions. PBR reactor packed with cilium type media, was efficient in nitrification. In condition of $0.038kg\;NH_4-N/m^3-media{\cdot}d$. 10~12 mg/L phenol conc. and 200~500 mg/L SCOD conc., nitrification efficiency was over 90% and phenol removal efficiency was over 98%.

• Journal of Soil and Groundwater Environment
• /
• v.13 no.1
• /
• pp.1-12
• /
• 2008

The purpose of this study is to characterize the hydrogeochemical characteristics of hot spring waters and to interpret the source of noble gases and the geochemical environment of the hot spring waters distributed along the eastern area of the Korean peninsula. For this purpose, We carried out the chemical, stable isotopic and noble gas isotopic analyses for eleven hot spring water and fourteen hot spring gas samples collected from six hot spring sites. The hot spring waters except the Osaek hot spring water show the pH range of 7.0 to 9.1. However, the Osaek $CO_2$-rich hot spring water shows a weak acid of pH 5.7. The temperature of hot spring waters in the study area ranges from $25.7^{\circ}C$ to $68.3^{\circ}C$. Electrical conductivity of hot spring waters varies widely from 202 to $7,130{\mu}S/cm$. High electrical conductivity (av., $3,890{\mu}S/sm$) by high Na and Cl contents of the Haeundae and the Dongrae hot spring waters indicates that the hot spring waters were mixed with seawater in the subsurface thermal system. The type of hot springs in the viewpoint of dissolved components can be grouped into three types: (1) alkaline Na-$HCO_3$ type including sulfur gas of the Osaek, Baekam, Dukgu and Chuksan hot springs, and (2) saline Na-Cl type of the Haeundae and Dongrae hot springs, and (3) weak acid $CO_2$-rich Na-$HCO_3$ type of Osaek hot spring. Tritium ratios of the Haeundae and the Dongrae hot springs indicate different residence time in their aquifers of older water of $0.0{\sim}0.3$ TU and younger water of $5.9{\sim}8.8$ TU. The ${\delta}^{18}O$ and ${\delta}D$ values of hot spring waters indicate that they originate from the meteoric water, and that the values also reflect a latitude effect according to their locations. $^3He/^4He$ ratios of the hot spring waters except Osaek $CO_2$-rich hot spring water range from $0.1{\times}10^{-6}$ to $1.1{\times}10^{-6}$ which are plotted above the mixing line between air and crustal components. It means that the He gas in hot spring waters was originated mainly from atmosphere and crust sources, and partly from mantle sources. The Osaek $CO_2$-rich hot spring water shows $3.3{\times}10^{-6}$ in $^3He/^4He$ ratio that is 2.4 times higher than those of atmosphere. It provides clearly a helium source from the deep mantle. $^{40}Ar/^{36}Ar$ ratios of hot spring water are in the range of an atmosphere source.

• Korean Journal of Microbiology
• /
• v.51 no.4
• /
• pp.355-363
• /
• 2015

The present work quantified the growth of young biofilm in a model distribution system that was fed with chlorinated drinking water at a hydraulic retention time of 2 h. Bacterial biofilms grew on the surface of polyvinyl chloride (PVC) slides at a specific growth rate of $0.14{\pm}0.09day^{-1}$ for total bacteria and $0.16{\pm}0.08day^{-1}$ for heterotrophic bacteria, reaching $3.1{\times}10^4cells/cm^2$ and $6.6{\times}10^3CFU/cm^2$ after 10 days, respectively. The specific growth rates of biofilm-forming bacteria were found to be much higher than those of bulk-phase bacteria, suggesting that biofilm bacteria account for a major part of the bacterial production in this model system. Biofilm isolates exhibited characteristic kinetic properties, as determined by ${\mu}_{max}$ and $K_S$ values using the Monod model, in a defined growth medium containing various amounts of acetate. The lowest ${\mu}_{max}$ value was observed in bacterial species belonging to the genus Methylobacterium, and their slow growth seemed to confer high resistance to chlorine treatment (0.5 mg/L for 10 min). $K_S$ values (inversely related to substrate affinity) of Sphingomonas were two orders of magnitude lower for acetate carbon than those of other isolates. The Sphingomonas isolates may have obligate-oligotrophic characteristics, since the lower $K_S$ values allow them to thrive under nutrient-deficient conditions. These results provide a better understanding and control of multi-species bacterial biofilms that develop within days in a drinking water distribution system.

• Journal of Korean Society of Disaster and Security
• /
• v.9 no.2
• /
• pp.63-75
• /
• 2016

For safe water supply, residual chlorine has to be maintained in tap-water above a certain level from drinking water treatment plants to the final tap-water end-point. However, according to the current literature, approximately 30-60% of residual chlorine is being lost during the whole water supply pathways. The losses of residual chlorine may have been attributed to the current tendency for water supply managers to reduce chlorine dosage in drinking water treatment plants, aqueous phase decomposition of residual chlorine in supply pipes, accelerated chlorine decomposition at a high temperature during summer, leakage or losses of residual chlorine from old water supply pipes, and disappearances of residual chlorine in water storage tanks. Because of these, it is difficult to rule out the possibility that residual chlorine concentrations become lower than a regulatory level. In addition, it is concerned that the regulatory satisfaction of residual chlorine in water storage tanks can not always be guaranteed by using the current design method in which only storage capacity and/or hydraulic retention time are simply used as design factors, without considering other physico-chemical processes involved in chlorine disappearances in water storage tank. To circumvent the limitations of the current design method, mathematical models for aqueous chlorine decomposition, sorption of chlorine into wall surface, and mass-transfer into air-phase via evaporation were selected from literature, and residual chlorine reduction behavior in water storage tanks was numerically simulated. The model simulation revealed that the major factors influencing residual chlorine disappearances in water storage tanks are the water quality (organic pollutant concentration) of tap-water entering into a storage tank, the hydraulic dispersion developed by inflow of tap-water into a water storage tank, and sorption capacity onto the wall of a water storage tank. The findings from his work provide useful information in developing novel design and technology for minimizing residual chlorine disappearances in water storage tanks.